I forgot to refrigerate my Wegovy – what happens now?

The 28-day rule: where the decision starts

Semaglutide (the active ingredient in Wegovy) is a protein-based medicine, and like most biologics it needs proper storage to stay effective. Refrigeration at 2–8°C is the default because it gives the medicine its maximum shelf life. But the semaglutide in a Wegovy pen does not instantly degrade the moment it leaves the fridge.

According to the Wegovy SmPC on the eMC, an unstarted or in-use pen can be kept at room temperature (up to 30°C) for up to 28 days. That is the cumulative total, not 28 days per episode out of the fridge. If you left your pen on the kitchen counter for a day, that day counts toward the 28. If you then popped it back in the fridge and forgot again a week later, those days count too. The clock runs continuously.

So the first practical question is: how many days in total has this pen spent outside the fridge? If the answer is fewer than 28, and the pen has not been exposed to anything extreme, you are still within the manufacturer's tested stability window. If you genuinely cannot remember, and the pen has been out for anything more than a couple of days, the cautious answer is to treat it as spent and speak to your prescriber about a replacement. Our page on whether Wegovy needs to be kept refrigerated gives a fuller breakdown of how the cold chain works and why it matters.

What actually ruins a pen, and what probably doesn't

A night on the bedside table is not the same as a pen left on a sun-facing windowsill all weekend. Temperature extremes at either end do real damage. Freezing degrades semaglutide; direct sunlight and temperatures above 30°C accelerate breakdown too. If your pen has been frozen (even briefly) do not use it. The same applies if the solution looks cloudy, discoloured or contains visible particles. A clear, colourless liquid is what you want to see.

A pen that has simply sat at a normal UK room temperature (typically 18–22°C) for a day or two is a much less dramatic situation than many people fear. If you are unsure exactly what that room-temperature allowance means in practice, our dedicated page on whether you need to refrigerate Wegovy walks through the guidance in plain terms and explains when keeping it out is acceptable.

One practical check that our prescribers at nume often suggest: look at the pen before you do anything else. Is the solution clear? Is the pen within its expiry date? Has it been above 30°C or frozen? If the pen passes those three checks and the total out-of-fridge time is within 28 days, the PIL supports using it. When the answer to any of those questions is uncertain, err on the side of caution.

Forgetting other steps, priming, prep and what else trips people up

Temperature storage is the most common concern, but it is not the only thing people forget. If you have also missed a step before injecting, our separate page on what to do if you forgot to prime your Wegovy pen covers that specific situation in full.

Missed a dose entirely? The NHS guidance on semaglutide is clear: if you forget an injection and more than five days have passed since your scheduled dose, skip it and resume on your normal day the following week. Never double up. Always check your PIL and speak to your prescriber if you are unsure, timing decisions like these are exactly what aftercare support is for.

Wegovy is a once-weekly subcutaneous injection taken from a pre-filled pen. Each pen contains four weekly doses, and if you are moving through the dose stages you may want to read our guide to the Wegovy green pen, which explains what to expect when you reach that particular device. A useful habit: return the pen to the fridge immediately after use, before you dispose of the needle in a sharps container, that way it is never sitting out longer than the injection itself takes.

When to contact your prescriber (or get medical advice)

If you used a pen that had been left out beyond 28 days, or one that was frozen or visibly compromised, and you experience any unusual or concerning symptoms, contact your prescriber or GP promptly. Reduced efficacy is the most likely consequence of a degraded pen, but it is worth flagging so your prescriber can account for it in your next review.

Any suspected adverse effect from a medicine you think may have been affected by storage can be reported directly at the MHRA's Yellow Card scheme, that reporting system exists for exactly this kind of situation and helps the regulator track real-world safety signals.

For broader questions about how Wegovy works, what to expect during treatment, and the full picture on what private treatment costs, our clinical team reviews every patient's file personally. If your storage situation has left you uncertain about your current dose or next steps, that is a conversation worth having before your next injection rather than after. You can find answers to specific storage questions, including whether you have to refrigerate Wegovy at all times or whether room temperature is ever acceptable, on our dedicated guidance pages. You can also check your eligibility and speak to our prescribers at any point.

The NHS page on semaglutide also has plain-language guidance on storage, missed doses and what to do if something goes wrong, worth bookmarking alongside your PIL.